The Gospel according to Merriam-Webster (please rise):—

nigh (nî) adverb
Etymology: Middle English, from Old English; akin to Old High German, adverb, nigh, preposition, nigh, after, Old Norse nigh.
Date, before 12th century

Definition
1 : near in place, time, or relationship — often used with on, onto, or unto
2 : NEARLY, ALMOST

(You may be seated.)

It is also listed in Merriam-Webster (lastest electronic version, by the way) as an adjective, a preposition, and a verb; and in compound form as well-nigh.

Although it may be considered an archaic term (from the 12 century or earlier), it is still very much in common usage in English speaking countries (but perhaps not in Chicago — or perhaps not to those who have a limited vocabulary)

Your welcome,

Don Firth