Quietly sullen and silently resentful.
Quietly sullen and silently resentful; moody, aloof, and inclined to pout and repel friendly advances.
Sulky is the pouting, withdrawn cousin of sullen — quietly out of temper, nursing a wordless grievance, moody and standoffish, and apt to rebuff any friendly overture. It is lighter and more childish than sullen, and more inward than petulant: where petulant snaps and whines aloud, sulky retreats into a wounded, silent pout that often half-invites being noticed and coaxed. It belongs to the family of anger and resentment but in a minor, almost theatrical key, closely allied to miffed and to “mope” and “pout.” It is the natural English neighbor of the Tagalog tampo, the affectionate sulking withdrawal that signals hurt while hoping to be drawn back — though English “sulky” is read more negatively, as petty standoffishness rather than a tender bid for reconciliation.
"Quietly sullen, silently resentful, moody and aloof, disposed to repel friendly advances," 1744, a word of uncertain origin with no record in Middle English. Connection has been suggested to the obsolete adjective "sulke" (hard to sell, 1630s) and to Old English asolcen "idle, lazy, slow" (past participle of aseolcan "become sluggish"). But words of similar meaning are often held to be imitative (compare miff, mope, pout). The carriage noun "sulky" (1756) is said to derive from the adjective, on the notion of standoffishness — a one-seat vehicle whose rider must ride alone.
Sulky appears suddenly in 1744 with essentially its modern sense and no Middle English ancestry, which is itself why its origin is uncertain. The "silently resentful, pouting" meaning has been stable since; the only notable development is the 1756 extension to the two-wheeled one-seat carriage, named for its solitary, standoffish character.
Origin uncertain: "sulky" has no Middle English record and appears abruptly in 1744; proposed links to obsolete "sulke" (hard to sell) and Old English asolcen "sluggish, lazy" are speculative, and many lexicographers treat such mood-words as imitative.