Fetid - fetor

Many British speakers of English write these words foetid and foetor. (The adjective fetid means having an offensive smell, often with connotations of 'rotting'. The noun fetor is 'an offensive smell'.)

OED prefers the spellings fetid and fetor, which have always been usual in the USA. OED points out that the words are derived from the Latin fētēre - and the Latin adjective fetidus was "often incorrectly written foetidus" - so if you use the (mis-)spellings with '-o-' you are making a very old error.

See also foetus - fetus.