[ane]

Germanic languages have a peculiarity in the words eleven and twelve, they stem from "one left" and "two left", respectively [0]. Cognates in German elf and zwölf, Swedish elv and tolv.

[0] "Cardinal Numerals: Old English from a Cross-Linguistic Perspective", http://bit.ly/1HhPzOB, page 161.

[RBerenguel]

Interesting. Worth noting Spanish, French, Catalan and probably some more connected languages I'm not so familiar with are irregular up to 16 (17 is akin to 10-7, whereas 11-16 follow other rules)

[riffraff]

left of what? (or from what?)

[fit2rule]

Okay now I get it. Start counting on your left hand. 1 .. 5, left-side, 6 .. 10, right-side. One-left, is "one full set of fingers, plus a left", repeating again, 11. Two left, 12. 3-ten, you change to a number count, because .. why not? It is self-documented .. and thus easier to teach. Maybe?

[ane]

Of ten. "One ... two ... [...] ten... and one and another.