The story
- Latin · derived fromfebris cum tertiānā
- Middle English · inherited fromtertiān
- English todaytertian
From Middle English tertiān, terciān, terciāne (adjective and noun), originally often as part of the collocation fever cum terciane, after Latin febris cum tertiānā. Compare the "third" essence of tertiary. By surface analysis, terti- + -an.
Etymology from Wiktionary, CC BY-SA 4.0.