I can remember my first theological debate. I was 7.
It was spring. My friend Mary Chris contended that Lent is called Lent because that's when you eat lentils. The Stepanoviches were Serbian Orthodox, and ate lots of lentils during Lent.
Clearly, there was a larger principle at stake here. To me, it seemed ridiculous that the larger thing should be named for the smaller. My automatic contrarian position was that lentils are named for Lent because that's when you eat them. (Not that anyone in my family ate lentils during—or even observed—Lent, mind you. But growing up in Pittsburgh, everyone knows what Lent is.)
Lent derives from the Old English word for “spring,” when the days lengthen. Had Harold won at Hastings, our four seasons today might be Winter, Lent, Summer, and Harvest.
Lentil is the diminutive of Latin lens, which meant “lentil.” (A lens, of course, is named for its lentil-like shape.) As we've been eating lentils for the last 12,000 years or so—since the end of the last Ice Age—it's not surprising that they should have their own name.
The words are unrelated. As in so many theological debates, it turns out that we were both wrong.