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.
More accurately, modern English and German come from the same root. A Proto-Germanic word for 15 developed into “fünfzehn” in German and “fifteen” in English.
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.
More accurately, modern English and German come from the same root. A Proto-Germanic word for 15 developed into “fünfzehn” in German and “fifteen” in English.