Ahead

google

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mid 16th century (originally in nautical use): from a-2 ‘in, at’ + head.

wiktionary

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a- +‎  head. Perhaps originally a nautical term, "beyond the  head (of a ship)", then drifting into more general English usage where it is used to describe something as being "in front of". 

etymonline

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ahead (adv.)

1620s, "at the head, in front," from a- "on" (see a- (1)) + head (n.) "front." Originally nautical (opposed to astern). Meaning "forward, onward" (the sense in go ahead) is from 1640s. To be ahead of (one's) time attested by 1837.