'second-rater' originates from English, specifically the words 'second' and 'rater', where 'second' ultimately comes from Latin 'secundus' meaning 'following' and 'rater' is an agent noun formed from the verb 'rate' (from Latin root 'ratiō-' related to calculation/assessment).

'second' entered English via Old French 'second' from Latin 'secundus'; the verb 'rate' developed from Latin-derived roots relating to calculation and assessment and produced the agent noun 'rater' by adding the English suffix '-er'. The compound 'second-rater' arose in modern English usage (notably in 20th-century academic and assessment contexts) to denote a secondary evaluator.

Initially, the elements meant 'following' (for 'second') and 'one who assesses' (for 'rater'); over time they combined to mean 'a person who gives a secondary or confirmatory evaluation', which is the current sense.