Folk etymology (also known as popular etymology) is an "explanation" of the meaning of a word based on its superficial similarity to other words, without analysing its morphological structure, documented history or scientifically reconstructible past forms.
Folk etymology may make people change the form of a word so that it would better match its popular rationalisation. For example, Old English sam-blind 'semi-blind' or 'half-blind' became sand-blind (as if 'blinded by the sand') when people were no longer able to make sense of the element sam 'half', and Old English bryd-guma 'bride-man' became bridegroom after the loss of the Old English word guma 'man' (compare French 'homme') rendered the compound semantically obscure. More recent examples are French (e)crevisse which became English cray-fish or asparagus which became sparrow-grass.
The pantry is not so called since it is or was used for storing pots and pans, but because it was originally a bread store (Old French paneterie, compare Spanish panaderia). (Room; see reference below)
In one example from non-sexist language, a feigned folk etymology was the source of neologisms like herstory to replace history. (To make it clear, the idea is that the story of mankind is his story but also her story; this is a play on words.)
- Adrian Room, Dictionary of True Etymologies, 1986, Routledge & Kegan Paul