Origins
The word 'flesh' is one of the fundamental body-terms of the English language, yet its deeper etymology remains a mystery. It descends from Old English 'flǣsc,' from Proto-Germanic *flaiską, and has cognates in every branch of Germanic: German 'Fleisch,' Dutch 'vlees,' Old Norse 'flesk,' Gothic 'mamsa' (which uses a different word — Gothic is the exception). But beyond Proto-Germanic, the trail grows cold. No convincing cognate has been established in any other Indo-European branch.
The most discussed proposal connects *flaiską to a PIE root *pleh₁k- or *pleh₁- (to tear, to split, to flay), which would make 'flesh' literally 'the torn-off thing' — meat named from the perspective of the butcher who strips it from the carcass. If this is correct, the word was born not in the language of anatomy but in the language of slaughter. The semantic path would be: 'to tear off' → 'the thing torn off' → 'meat' → 'the soft tissue of the body.' This etymology is plausible but unproven.
In Old English, 'flǣsc' served a dual function that it retains today: it meant both the tissue of the living body and the meat of animals prepared for eating. This dual meaning is shared with German 'Fleisch' but contrasts sharply with French, which distinguishes 'chair' (flesh of the body) from 'viande' (meat for eating). The English language thus preserves an older Germanic conceptual unity between the living body and the edible carcass.
Old English Period
The theological weight of 'flesh' is immense. In Christian tradition, heavily shaped by the Latin Vulgate's use of 'caro' (flesh), 'the flesh' became a technical term for the fallen, sinful nature of humanity — the desires of the body opposed to the aspirations of the spirit. Paul's epistles set up the opposition between 'flesh' and 'spirit' (Greek 'sarx' vs. 'pneuma'), and Old English biblical translations rendered 'sarx' as 'flǣsc,' giving the word its enduring moral charge. 'The sins of the flesh,' 'flesh and blood,' 'the Word made flesh' — all these phrases carry the theological freight of two millennia.
The Scandinavian cognates underwent a striking narrowing. Swedish 'fläsk' and Norwegian 'flesk' both mean specifically 'pork' or 'bacon,' not flesh in general. This semantic narrowing reveals that for the medieval Norse, pig meat was the prototypical, default flesh — so dominant that the generic word became specialized. The same process occurred in reverse in English, where 'meat' (which originally meant 'food' in general, as in 'sweetmeat') narrowed to mean 'animal flesh.'
The adjective 'fleshy' (having much flesh) dates from the fourteenth century. 'Fleshly' (carnal, sensual) is older, from Old English 'flǣsclic,' and carries the moral overtones of the theological tradition. The compound 'flesh-wound' (a wound not reaching bone or vital organs) dates from the sixteenth century — a term born on the battlefield, where the distinction between a wound in the flesh and a wound in the bone was the difference between recovery and death.