Old English fiftyne, from fif "five" (from PIE root *penkwe- "five") + tyne (see -teen). For vowel shift, see met (v.). Cognate with Old Saxon fiftein, Old Frisian fiftine, Old Norse fimtan, Swedish femton, Dutch vijftien, German fünfzehn, Gothic fimftaihun "fifteen." French quinze, Italian quindici "fifteen" are from Latin quindecim (from quinque "five;" see quinque-; + -decim (see -teen). The number of players forming a side in rugby.