The word "klette" mentioned in the OP is also in "English" English too, though you don't hear it so often now. It's the word "clot" meaning a gormless, stupid person. Like "berk" and "pillock".
"Thole" - to endure, but also accept something. The verb used for "to bite into a shit sandwich".
Example- "Da', can we no turn the heating oan in the hoose? Ah cannae feel ma feet" - "Ach, dry yer eyes son. Thole it."
"Roaster" - a very 1990s/early 2000s insult meaning "a repugnant, dreadful person, probably a bit crazy and full of misconceived notions about things, like a really bigoted football fan"
Example - "Did ye see George Galloway on TV the other night? What a total fucking roaster."
"Fud" - an insult and noun meaning both "a vagina" and "someone who is very, very stupid".
Example - "Here, is Africa a country or a continent?" - "Don't be such a fud, man"
"Bam" - Glaswegian insult and noun usually meaning a person who is "Below Average Mentality". In more common usage across Scotland people say "bampot". In my own usage (I say bam, not bampot) it tends to mean a wastrel, like a washed up, middle aged, drug addicted/alcoholic failed rocker who hangs around in pubs, thinks he's really funny and always tries to be the centre of attention. Or a guy who goes to pubs wearing an Old Firm shirt and picks fights. Also used as a verb in the phrase "to bam someone up".
Examples - "Fuck off ya bam" - "Who're you calling a bam, ya bam?" - "Yer maw's a bam" - "Ah'll slash ye ya prick"
"Fucksake man John Paul's pure bammin me up, man" - "Here, John Paul, gonnae stop bammin me up, man?"
"Ged" - A very unusual word unique to the rural, Highland part of Perthshire where I live. Said by lower-class farmers. This word has no meaning other than to fill space in a conversation and make sentences end better. I do not know where it comes from.
Example - "Aw right, ged, whit's the craic, like?" - "Nae bad, like, whit aboot yersel, ken?" - "Ach, braw, min" - "Aye, ged.".
"Scud" - a verb meaning to hit or strike, the object usually being a person. The motion is hard and without finesse, blunt.
Example - "Gonnae no scud me er the heid wi that 'hing?" - "Ah jist scudded the c*nt er the back ae the heid wi a brick"
"Creik o day" - an Aberdeenshire/Doric/North East Scottish expression meaning dawn. Basically "crack of day".
Example - "At the creik o day ah'm oot in the fields, min"
"Braw" - Very good, delightful or beautiful. Once common across Scotland, now most commonly heard in the Borders, the Highlands or the North East.
Example - "Aye, wu've goat a braw wee sholtie comin' the day fae the merkit, ah'll put her in the fields the morra" - "Och, that soonds braw, min".
"Moan 'en" - An urban battle cry said in pubs before fights, literally a contraction of "come on then".
"Fuck Rangers! Celtic till I die! Oo aah up the 'RA!" - "MOAN 'EN YA BASS"
"FUCKINSAYTHATTAEMAEYEAPRICK" - incomprehensible expression uttered usually in response to "moan 'en" or as a final exclamation in a "yer maw's a ride" type of insulting match. Precedes the smashing of a pint glass into the offending party's face.
Example - "Ah shot yer cat" - "Ah stabbed yer dug" - "Yer da' rakes bins" - "Yer maw's a ride" - "FUCKINSAYTHATTAEMAEYEAPRICK"
"Bonnie" - something that is visually nice and pretty, possibly beautiful.
Example - "Noo, ma wee lassie, ah'll put ribbons in yer hair. It'll mak ye look bonnie."
"Sair fecht" - literally a "sore fight" i.e. hardship. My great grandfather used to say this a lot. Often said in the expression "Life's an awfy sair fecht fer a loaf o breid" i.e. "Life is an awfully sore fight for a loaf of bread".
Example - "Ah'm gutted ah didnae get the job, da'" - "Aye, son, life's a sair fecht".
"Craic" - Pronounced "crack". A Scottish, Irish and Northern Irish expression meaning both banter and also fun, the kind of fun to be had in a pub or at a party. Can also be used as an alternative to "shits and giggles" if one says "A just did it fer the craic". Mostly in the Highlands and where I live.
Example - "Here, lad, did ye go tae Tam's retirement party the ither night?" - "Aye, it was guid craic, like"
"Patter" - Glaswegian slang meaning "witty banter". To have good patter is key to being liked and having good relationships in the city. Conversely, to have lacklustre patter is truly awful and will make you seem like a bit of a fud. This is called having "patter like watter" i.e. to be unfunny.
Example - "Fucksake man ah'm lovin this c*nt's patter man"
"Yer patter's like watter, mate"
"Sook" - a brown noser, usually, but can also be used when describing a baby, child or pet's behaviour if they want a lot of love and affection. Also a verb meaning to brown nose - "sooking up tae" - obviously coming from the Scottish pronunciation of "suck".
Example - "Did ye see Jock sookin' up tae the the boss the ither night? Fuckin disgustin man" - "The cat's awfy sooky the day, is he no? Is he wanting fed?
"Crivvens" - an exclamation and adjective. As an exclamation it is the equivalent of "Oh my goodness!" but somewhat worse, as an adjective it means very, very ugly.
Example - "Crivvens! Yer maw's crivvens, min"
"Ned" - "Non-Eduated-Delinquent" - the Scottish equivalent of a "chav" i.e. an unpleasant, boorish, underclass person.
Example - "Did ye see aw they neds drivin' aboot in their suped up purple subaru imprezas wi the gold hubcabs?"
"Fanny" - a woman's vagina, but also a very very stupid, unthinking person.
Example - "John Paul's being a total fanny, man. Gonnae tell him tae stop shoutin at the Huns? He'll get us stabbed"
"Teuchter" - a rural yokel, invariably from the Highlands, Islands or central or North-East Scotland. For Glaswegians this means everyone outside of Glasgow. I am a teuchter.
Example - "Aw right, ged, whit's the craic, like?" - "Fuck off ya teuchter bastart"
"Choon" - Scottish dialectal pronunciation of "tune". An exclamation or noun meaning a good piece of music. A modern expression usually uttered by young, working class guys at a rave or something.
Example - "Choon!" - "This fucking choon, man! This fucking CHOON!"
"Stot" - pronounced "stote" or "stoat". A verb usually meaning to throw something at someone/something and hit the target with a degree of impact. Also when conjugated as "stottin" it becomes an adjective, pronounced "stoating", which means something is very hard but almost invariably food which has been undercooked, like when you don't boil potatoes properly.
Example - "Ah'll stot this stane aff yer heid" - "These tatties are stottin"
"Stramash" - A Highland word meaning a frenzied calamity, row, uproar or argument.
Example - "There was an awfy stramash up at the ferm the ither day oer the yows and whaur they shuid be pit fer the winter. It shouldn'tae but they came tae blows, like. A daft thing."
"Heidthebaw" - an insult, coming from a very, very bizarre Scottish contraction of "head the ball" i.e. someone who headbutts footballs. This means someone who is a nutjob.
Example - "If ye dinnae like thon, ye're a heidthebaw, min"
And I can keep going, I've got an infinite supply of words. Truly endless.