ガス
ガス · gasu · JLPT N4 · noun
gas
⛽ ガス = gasu: English gas plus a trailing u — a loanword via Dutch gas
Japanese borrowed the word from Dutch gas, the same root as the English word. Katakana cannot end a syllable on s, so a soft u is added: ga-su. Say gas, then let a faint u trail off.