Meaning

adjective unhealthy looking

adjective somewhat ill or prone to illness

originFrom Middle English seekly, sekely, siklich, sekeliche, equivalent to sick + -ly. Possibly a modification of Old English sīcle (“sickly”) and/or derived from Old Norse sjúkligr (“sickly”). Cognate with Dutch ziekelijk, Middle High German siechlich, Danish sygelig, Swedish sjuklig, Icelandic sjúklegur. The verb is from the adjective.

Etymology from Wiktionary, CC BY-SA 3.0