I have long known this word to mean "countrified" but only just now encountered the etymology:
Source: Webster's Revised Unabridged Dictionary (1913)

Bucolic \Bu*col"ic\, n. [L. Bucolic[^o]n po["e]ma.]
A pastoral poem, representing rural affairs, and the life,
manners, and occupation of shepherds; as, the Bucolics of
Theocritus and Virgil. --Dryden.
Bucolic \Bu*col"ic\, a. [L. bucolicus, Gr. ?, fr. ? cowherd,
herdsman; ? ox + (perh.) ? race horse; cf. Skr. kal to drive:
cf. F. bucolique. See Cow the animal.]
Of or pertaining to the life and occupation of a shepherd;
pastoral; rustic.