English
heat-seeking
From heat + seeking.
Proto-Indo-European *keHy- ‘heat’
Proto-Germanic *haitį̄
Proto-West Germanic *haitī
Old English hǣtu
Middle English hete ‘heat’
English heat
Today it means
adj Of a missile or rocket, able to detect and follow the heat emitted by an aircraft engine or rocket.
Language periods are conventional ranges, not dates for this word.
Etymograph / heat-seeking