Where does “fiughertān” come from?

fiughertān (Old Swedish) comes from Old Norse fjugurtán, from Old Norse fjórtán, from Proto-Germanic fedurtehun, from Proto-Germanic fedwōr, from Proto-Indo-European kʷetwóres, from Proto-Indo-European kʷe- — and.

Ancestry of “fiughertān”, step by step

Step	Language	Word	Meaning
1	Old Norse	fjugurtán	—
2	Old Norse	fjórtán	fourteen
3	Proto-Germanic	fedurtehun	fourteen
4	Proto-Germanic	fedwōr	four
5	Proto-Indo-European	kʷetwóres	four
6	Proto-Indo-European	kʷe-	and

Words derived from “fiughertān”

fjorton
fjortis
fjortonhundratal
fjortonårig
fjortonåring
fjortis

Every word from Proto-Indo-European kʷe- →Every word from Proto-Indo-European kʷetwóres →Every word from Proto-Germanic fedwōr →