The most famous use of the word sleekit is Burns’s ubiquitous-for-a-reason (you can listen to me talking about my love for the poem with the wonderful Ryan van Winkle many years ago for the Scottish Poetry Library (the one true SPL) podcast if you click here) ‘Tae a Moose’, which begins,
Wee, sleekit, cow’rin, tim’rous beastie,
O, what a panic’s in thy breastie!
In the context of the poem, the word ‘sleekit; is used in the adjectival form, meaning smooth, without roughness. The word consists of ‘sleek’ and the suffix ‘-it’ which is how to denote the past-tense in Scots, the equivalent of ‘-ed’ in English (although ‘-ed’ is obviously also used in Scots now too). We have the word ‘sleek’ in English to mean smooth or glossy, though it comes from the Scots, who got it from the Middle Flemish sleec/sleic which meant even with the top of a vessel. So when you fill your tea right to the brim, that is a sleek measure.
Sleekit is also used to describe someone who is a bit slimy, who tends to wheedle their way into positions that are advantageous to them, maybe who aren’t to be trusted. You can see how sleek’s progression from a measurement that involves smoothing across the top of a cup or barrel, leads to the word being used to refer to something that is smooth or glossy in appearance (like a slinky wee moose wheeching away from a dangerous plough). You can also see how it can be expanded to refer to a person who is ‘oily, fawning, or deceitful’. There is a similar link between the English word ‘smooth’ meaning free from bumps, and the descriptor of a person who is a bit slimy and falsely flattering, ‘He’s a bit smooth, that one’.
This is uttterly true: as I am writing this I have my preferred digital music devise (iPhone™) on shuffle™ and on came Michael Jackson’s Smooth Criminal! The murderer in that song is certainly sleekit. Also, in a side Scottish-Michael Jackson fact, I used to think the lyrics were ‘Annie get your oatcake, get your oatcake Annie.’ A national oat-based snack AND the suffix ‘-ie’ as a familiar nick name? More like Michael MacJackson!