Where does “usul” come from?

usul (Maltese) comes from Arabic وصول, from Arabic وَصَلَ, from Arabic ص — Y, unknown variable.

Ancestry of “usul”, step by step

StepLanguageWordMeaning
1Arabicوصولverbal noun of وَصَلَ; arrival
2Arabicوَصَلَto connect; to arrive, connect; to arrive, to...
3ArabicصY, unknown variable
Every word from Arabic ص →Every word from Arabic وَصَلَ →Every word from Arabic وصول →