Seer

google

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Middle English: from see1 + -er1.

wiktionary

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see +‎  -er(“agent suffix”). 

See sihr.

etymonline

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seer (n.)

late 14c., "one to whom divine revelations are made," agent noun from see (v.). Originally rendering Latin videns, Greek bleptor (from Hebrew roeh) in Bible translations (such as I Kings ix.9). Literal sense of "one who sees" is attested from early 15c.