'expenseable' originates from English, specifically formed from the noun 'expense' combined with the adjectival suffix '-able' (ultimately from Latin '-abilis'), where 'expense' derives from Latin 'expensa' (from 'expendere', meaning 'to weigh out, pay out').

'expense' entered English via Old French/Middle English (e.g. Old French 'expense', Medieval Latin 'expensa') and came to mean 'an outlay or cost'; adding the productive English suffix '-able' created 'expenseable' to mean 'able to be treated as an expense'.

Initially 'expense' referred to an outlay or cost; over time the derived adjective 'expenseable' has come to mean specifically 'eligible to be recorded/claimed as an expense' (a policy/tax/administrative qualification).