c. 1300, "entrance, arrival," literally "a coming in;" see in (adv.) + come (v.). Perhaps a noun use of the late Old English verb incuman "come in, enter." Meaning "money made through business or labor" (i.e., "that which 'comes in' as payment for work or business") first recorded c. 1600. Compare German einkommen "income," Swedish inkomst. Income tax is from 1790, introduced in Britain during the Napoleonic wars, re-introduced 1842; in U.S. levied by the federal government 1861-72, authorized on a national level in 1913.