'charwoman' is formed in English from 'char' (meaning an odd job or household task) + 'woman'.

'char' comes from Middle English 'chare' meaning 'a turn, task'; the compound 'charwoman' appears in Early Modern English (17th century) to mean a woman who does household chores.

Initially it specifically meant 'a woman employed to do odd household jobs'; the basic meaning has remained similar but the word has become dated/archaic in modern usage.