alight (v.)

"to descend (from horseback, etc.), dismount," Old English alihtan "alight," originally "to lighten, take off, take away," from a- "down, aside" (see a- (1)) + lihtan "get off, make light" (see light (v.)). The notion is of getting down off a horse or vehicle, thus lightening it. Of aircraft (originally balloons) from 1786. Related: Alighted; alighting.

"on fire," early 15c., apparently an adjectival use of Middle English aliht, past participle of verb alihton (Old English on-lihtan, obsolete from 17c.) "to light up, set light to," also "to shine upon" (see a- (1) + light (n.)). Now regarded as parallel to afire, ablaze, etc.