hereat is an archaic compound from here (Old English hēr) + at (Old English æt); used to mean 'at this point' or 'because of this'. Morphologically, the word is best read through the components named in the history, with the modern spelling preserving a compound structure rather than a single unanalyzable stem. In present English, the adverb sense is "at this point or because of this (archaic)", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as here, whereat, thereat, and hereto. Its semantic neighborhood includes hereupon, thereupon, and whereat, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Old English hēr and Old English æt.