Ooh, forgot about that one so yeah, totally fair game.

Came to post this, of course someone beat me to it.

Hey, we have a poster of this up in our dining room

To be fair English has a lot of German. The “teen” sound almost certainly comes from the sound “zehn”. It’s pretty easy to hear how fünfzehn und sechszehn eventually become fifteen and sixteen. We’re more or less saying five ten just kinda mushed together.