Pension
late Middle English (in the sense ‘payment, tax, regular sum paid to retain allegiance’): from Old French, from Latin pensio(n- ) ‘payment’, from pendere ‘to pay’. The current verb sense dates from the mid 19th century.
wiktionary
From Middle English pension, from Anglo-Norman pencione, Old French pencion, and their source, Latin pēnsiō, pēnsiōnem(“payment, weight, rent, compensation”), from the participle stem of pendere(“to weigh”). Doublet of pensione.
etymonline
pension (n.)
late 14c., pensioun, "payment for services," especially "a regular reward or annual payment out of a will or benefice" (early 14c., in Anglo-Latin), from Old French pension "payment, rent" (13c.) and directly from Latin pensionem (nominative pensio) "a payment, installment, rent," from past-participle stem of pendere "to hang, cause to hang; weigh; pay" (from PIE root *(s)pen- "to draw, stretch, spin"). For the financial sense of the Latin verb, see pound (n.1).
Meaning "regular payment to a person in consideration of past service" is from 1520s, hence "periodic payment made to a person retired from service on account of age or disability" (originally especially government pay to soldiers and sailors). Meaning "boarding house, boarding school" is attested from 1640s, from a sense in French based on the meaning "money paid for board," and in English it is usually in reference to places in France or elsewhere on the Continent.
pension (v.)
1640s, "to live in a pension," from pension (n.) or else from French pensionner. Meaning "to grant a pension" is from 1702. Related: Pensioned; pensioning.