The other day I posted about how English still has vestiges of a base-12 counting system, shown in part by the fact that hundred used to refer to 120 rather than 100. Many, many people commented on this asking why it didn’t mean 144 (12×12) instead of 120.
The reason for this is that Old English speakers were influenced by both the base-12 system of their Germanic ancestors, and the base-10 system that was used in writing, and was borrowed from the Roman empire and Catholic church.
It’s not at all uncommon for languages to have mixed systems like this. French, for example, shows vestiges of a base-20 system for numbers from 60–80 (e.g. soixante-dix ’70’ is literally ‘sixty-ten’ and quatre-vingt ’80’ is literally ‘four-twenty’). Languages will often have a pivot at a smaller number, using that smaller number as a base until reaching the base. Igbo (a Niger-Congo language spoken in Nigeria), for example, is base 20, but uses base 10 for numbers smaller than twenty. Here’s the Igbo word for 32, literally ‘twenty and ten and two’: