Etymology: Cognate with Old Saxon kostōn , Old High German kostōn , kostēn (Middle High German, German kosten to try, to taste (food)), Old Icelandic kosta , Old Swedish, Swedish kosta (now rare), all in senses ‘to try’, ‘to tempt’ < the Germanic base of cost n.² In β. forms apparently with alteration after -en suffix⁵; compare forms of costning n.¹In Old English, forms with -n- (see β. forms) are later and are especially typical of the writings of Ælfric. The prefixed forms gecostian , gecostnian (compare y- prefix) are also attested; compare also acostian to try, test, prove (compare a- prefix¹), forecostian (rare) to profane (compare fore- prefix), wiþcostian (rare) to reprove (compare with- prefix).

Etymology: < Anglo-Norman and Old French coster cost v., apparently with alteration of the ending after -en suffix⁵, perhaps by association with the earlier, unrelated homonym costen v.¹ (see note). Compare later cost v. Perhaps compare the nouns Old Icelandic kostnaðr , Old Swedish kostnadher (Swedish kostnad ), Old Danish kostnædh , and (with added prefix) Danish bekostning , all in sense ‘expense’, but in these -n- is apparently part of the nominal suffix (compare Old Icelandic kosta cost v.). Parallel verbs with -n- do not appear to be attested in other Germanic languages.Although costen v.¹ and costen v.² are usually quite distinct semantically, early use with reference to hardship in figurative contexts (compare quots. ?c1225¹, ?c1225²) could have reinforced the association.