Almighty
Old English ælmihtig (see all, mighty).
wiktionary
From Middle English almyghty, almighty, from Old English ælmihtiġ(“all-powerful”), from Proto-Germanic *alamahtīgaz, equivalent to al- + might + -y.
etymonline
almighty (adj.)
Old English ælmihtig "all-powerful," also a by-name of God; compound of æl (see all) + mihtig (see mighty); common Germanic (cognates: Old Saxon alomahtig, Old High German alamahtic, German allmächtig, Old Norse almattigr), perhaps an early Germanic loan-translation of Latin omnipotens (see omnipotent). Originally only of deities; general use is by late 14c.
The almighty dollar, that great object of universal devotion throughout our land. [Washington Irving, "The Creole Village," in The Knickerbocker, or New-York Monthly Magazine, November 1836]
Related: Almightily; almightiness. A 15c. text translates omnipotencia with allmyghtyhede "almightihood."