"broad, shallow vessel of metal used for domestic purposes," Middle English panne, from Old English panne, earlier ponne (Mercian) "pan," from Proto-Germanic *panno "pan" (source also of Old Norse panna, Old Frisian panne, Middle Dutch panne, Dutch pan, Old Low German panna, Old High German phanna, German pfanne), probably an early borrowing (4c. or 5c.) from Vulgar Latin *patna. This is supposed to be from Latin patina "shallow pan, dish, stew-pan," from Greek patane "plate, dish," from PIE *pet-ano-, from root *pete- "to spread."
But both the Latin and Germanic words might be from a substrate language [Boutkan]. Irish panna probably is from English, and Lithuanian panė is from German.
The word has been used of any hollow thing shaped somewhat like a pan; the sense of "head, top of the head" is by c. 1300. It was used of pan-shaped parts of mechanical apparatus from c. 1590; hence flash in the pan (see flash (n.1)), a figurative use from early firearms, where a pan held the priming (and the gunpowder might "flash," but no shot ensue). To go out of the (frying) pan into the fire "escape one evil only to fall into a worse" is in Spenser (1596).
Greek god of shepherds and flocks, woods and fields, with upper body of a man and horns and lower part like a goat, late 14c., from Latin, from Greek Pan. Klein and others suggest the Greek word is cognate with Sanskrit pusan, a Vedic god, guardian and multiplier of cattle and other human possessions, literally "nourisher," from a PIE root *peh- "to protect," but others doubt this.
His worship originated in Arcadia and gradually spread throughout Greece. The similarity to pan "all" (see pan-) led to his being regarded as a general personification of nature. He was fond of music and dancing with the forest nymphs; the pan-pipe, which he invented and upon which he played, is attested by that name in English from 1820.
"to wash (gravel or sand) in a pan in search of gold," 1839, from pan (n.); thus to pan out "turn out, succeed" (1868) is a figurative use (the expression in the literal sense of "yield gold when washed out in a pan" is by 1849). The meaning "criticize severely" is from 1911, probably from the notion in contemporary slang expressions such as on the pan "under reprimand or criticism" (1923), probably from the notion of being roasted or fried. Related: Panned; panning.