'antiestrogen' originates from the Greek prefix 'anti-' (Ancient Greek 'anti') meaning 'against' and from 'estrogen' (from New Latin 'oestrogen'), where the root 'oistros' in Greek originally meant 'gadfly' or 'sexual passion'.

'estrogen' changed from Neo-Latin 'oestrogen' (coined in the 20th century from Greek 'oistros') and eventually became the modern English word 'estrogen'; 'anti-' was prefixed in English to indicate opposition, producing 'antiestrogen' and then the plural form 'antiestrogens'.

Initially, terms related to 'oistros' referred to sexual frenzy or strong biological drives; over time 'estrogen' came to denote the specific class of hormones regulating estrus and reproductive functions. 'Antiestrogen' originally meant simply 'against estrogen' and evolved into a technical term for drugs that block estrogen action.