Old English -ælfen (n.) "an elf or fairy," usually a female one (see elf). Not a pure adjective in Middle English (elvish was used), but used in phrases such as elven land (c. 1300). Apparently revived as an adjective by Tolkien (1937).
elucidation
elude
elusion
elusive
elution
elven
elver
Elvira
elvish
Elysian
Elysium