'forty-nine' originates from Old English elements for the two numbers: 'forty' from Old English 'feowertig' (formed from 'feower' meaning 'four' + '-tig' meaning 'tens') and 'nine' from Old English 'nigon' (meaning 'nine').

'forty' evolved from Old English 'feowertig' through Middle English forms such as 'forti' to the modern 'forty', and 'nine' evolved from Old English 'nigon' to Middle English 'nine'; the compound 'forty-nine' is a straightforward combination of these numeral words in modern English.

Initially each element referred to the same numeric values ('four tens' and 'nine'); over time the individual words stabilized in form, and their combined use has consistently meant the number 49.