formerly also empeach, late 14c., empechen, "to impede, hinder, prevent;" early 15c., "cause to be stuck, run (a ship) aground," also "prevent (from doing something)," from Anglo-French empecher, Old French empeechier "to hinder, stop, impede; capture, trap, ensnare" (12c., Modern French empêcher), from Late Latin impedicare "to fetter, catch, entangle," from assimilated form of in- "into, in" (from PIE root *en "in") + Latin pedica "a shackle, fetter," from pes (genitive pedis) "foot" (from PIE root *ped- "foot").

In law, at first in a broad sense, "to accuse, bring charges against" from late 14c.; more specifically, of the king or the House of Commons, "to bring formal accusation of treason or other high crime against (someone)" from mid-15c. The sense of "accuse a public officer of misconduct" had emerged from this by 1560s. The sense shift is perhaps via Medieval Latin confusion of impedicare with Latin impetere "attack, accuse" (see impetus), which is from the Latin verb petere "aim for, rush at" (from PIE root *pet- "to rush, to fly").

The Middle English verb apechen, probably from an Anglo-French variant of the source of impeach, was used from early 14c. in the sense "to accuse (someone), to charge (someone with an offense)." Related: Impeached; impeaching.