The Abercromby surname comes from the place in Fife. Here we have a falcon and the Latin motto 'Petit Alta'.

The meaning behind this is nice and straightforward: the Falcon is a reference to Alexander Abercromby of Birkenbog, who lived from 1584 to 1666. He was 'Grand Falconer of Scotland' appointed by King Charles I. The motto plays on this, it literally means 'he/she/it seeks/strives for the lofty/high [things]'. No obvious origin for the Latin there - just riffing on things flying.
The crest in the 1720s was an oak tree with acrons with the motto Tace (see Nisbet’s System of Heraldry). This had been the crest of the chiefly line, Abercromby of that Ilk, but on their extinction the arms passed to the Arbercrombys of Birkenbog. They initially kept the oak tree, but by 1792 they updated the crest to the falcon and new motto. The registration made direct reference to the royal falconer (R.R. Stoddart, Scottish Arms being a Collection of Armorial Bearings 1370-1678, p.55)
Other Abercromby crests include Abercrombie of Fitternier, which had a cross croslet fitche and the motto ‘In Cruce Salus’, then Abercromby of Glasshaugh had a bee with the motto ‘Vive ut vivas’.
For Alexander Abercromby, see Alistair and Henrietta Tayler, eds, The Valuation of the County of Aberdeen for the Year 1667, Aberdeen, Third Spalding Club, 1933, p.122.
MKP 10 June 2020