Not unlike how in the trades, a tee is T-shaped, a wye is Y-shaped, a delta is Δ-shaped. Spelled-out letters aren't always geometric metaphors, but it's a thing.

Then you've got the first syllable of Ω (omega) being a homophone of Ohm, for what that's worth. From there we have ℧ (mho) for conductance... It's all quite clever. But I digress; I'll get back to emceeing and deejaying, cueing these elpees after a quick pee, okay?

Different fonts use different lengths (sometimes en dash is the width of an uppercase “N” instead of lowercase, sometimes it’s half of the em dash which itself is `1em` which may or may not equal the width of the “M”...) But it’s a good way to remember that indeed, yeah!