Abarim Publications' online Biblical Hebrew Dictionary
Scholars insist that there are three separate roots אנש ('nsh) and one root איש ('ysh), which have nothing to do with each other. BDB Theological Dictionary acknowledges the few who have assumed that there are certainly relationships, but decrees a single ancestral root "impossible".
This may be theoretically true, but we may as readily assume that the Hebrew authors and audience were more persuaded by these words' similarities than by their differences:
The verb אנש ('anash) means to be sick or weak (Job 34:6, 2 Samuel 12:15, Micah 1:9). This verb occurs about a dozen times in the Old Testament, and has no derivatives.
The root אנש ('nsh) isn't used as verb in the Bible, but in cognate languages it means to be inclined to, friendly or social. It yields one derivative, the masculine noun אנוש ('enosh), meaning man or mankind (Job 28:13, Psalm 8:4, Isaiah 24:6). This word is one of a few to mean man, and 'enosh seems to indicate man without any special characteristic; hence the name Enosh
Both HAW Theological Wordbook of the Old Testament and BDB Theological Dictionary quote theories that put this root and the previous one together, and 'enosh may denote man as frail and helpless creature. Perhaps it even teaches that the strength of society in general is a direct result of the frailty of the human individual, which is an idea also expressed by the Greek words ψυχη (psuche), meaning soul or needy thing, and πνευμα (pneuma) meaning spirit or synchronously moving things. Perhaps mysterious texts such as Revelation 13:3 should be understood in part against the backdrop of this principle.
Some scholars have suggested that the mysterious noun אש ('esh), meaning fire, was derived from this root, but others refute this (reports BDB Theological Dictionary).
The third root אנש ('nsh) is again unused in the Bible, but in cognate languages it may means soft or delicate. Its sole derivative is the feminine noun אשה ('ishsha), meaning woman or wife. Since the Bible views societies as female individuals (i.e. mother Babylon, or the Bride of Christ), and women are generally weaker than man, here at Abarim Publications we see much reason to assume one single core idea behind these roots, even if the roots themselves are separate in theory.
And then there is root איש ('ysh) which yields the masculine noun איש ('ish), meaning man or mankind. It's obviously one of a few Hebrews words that can be translated as 'man' but appears to be most alike our English word 'man'. It differs from אדם ('adam), or 'corporeal one' and the noun אנוש ('enosh), or 'human' in that איש ('ish) regards man as an individual and that mostly in some specific function. In constructions like "man of the earth" (Genesis 9:20) or "man of God" (Deuteronomy 33:1), this word איש ('ish) is used. This word is also the common word for husband.