alike

The adjective comes from a conflation of several different terms:

Middle English alich, alych, alyke, a Late Middle English development from earlier Middle English anlich, anlyke, from Old English onlīċ, anlīċ. Compare German ähnlich.

The borrowed Old Norse cognate of the same word, álíkr, ultimately yielding similar Late Middle English forms.

Middle English ylich, ylych, ilich, ylik, ylike, ȝelic, from Old English ġelīċ (“like; alike; similar; equal”), from Proto-West Germanic *galīk, from Proto-Germanic *galīkaz (“alike, similar”). Cognate with Scots elyke, alyke (“like, alike”), Saterland Frisian gliek (“like, alike”), West Frisian lyk, gelyk (“like, alike”), Dutch gelijk (“like, alike”), German Low German liek, gliek (“like, alike”), German gleich (“equal, like”), Danish lig (“alike”), Swedish lik (“like, similar”), Norwegian lik (“like, alike”), Icelandic líkur (“alike, like, similar”). Equivalent to a- (Etymology 3) +‎ like. Compare also West Frisian allyk (“all the same, alike”).

Similarly, the adverb also comes from a conflation of several different terms:

Middle English aliche, alyche, alyke, a Late Middle English development from earlier Middle English anliche, anlyke, from Old English onlīċe, anlīċe.

Additionally Middle English oliche, olike, ultimately from the Old Norse cognate of the same word, álíka.

Middle English yliche, ylyche, iliche, ylike, ȝelice, from Old English ġelīċe (“alike, similarly”).