Did some research and lilscamp you are soo right... it is definitely always "lavender". But I found something interesting in my search which makes perfect sense and I wish I had thought of before:

Lavender

\Lav"en*der\, n. [OE. lavendre, F. lavande, It. lavanda lavender, a washing, fr. L. lavare to wash; cf. It. lsavendola, LL. lavendula. So called because it was used in bathing and washing. See Lave. to wash, and cf. Lavender.] 1. (Bot.) An aromatic plant of the genus Lavandula (L. vera), common in the south of Europe. It yields and oil used in medicine and perfumery. The Spike lavender (L. Spica) yields a coarser oil (oil of spike), used in the arts.