Flip through a pile of daily crosswords and the four-letter fill that keeps sneaking up is 'SCOT'. I find it because crossword constructors love short, unambiguous demonyms for compact clues, and 'SCOT' fits neatly into lots of grids. When the clue reads 'Highlander' without extra context, setters often intend the simple nationality read: a Scot from Scotland’s Highlands. It’s crisp, familiar, and plays nicely with common crossing words.
That said, I’ll admit I’ve seen 'GAEL' show up when the setter wants an ethnic or cultural angle—especially if the clue hints at Gaelic language or tradition. Plural forms like 'SCOTS' or 'GAELS' pop in too, but for sheer frequency and utility, my solving experience leans heavily toward 'SCOT'. It’s one of those little crossword habits that becomes comforting after you notice it a few times; I grin when a 4-letter 'Highlander' slot appears, already half-guessing the fill.