The etymology of this specifically Assyrian word (Kogan 2006a:184, as opposed to Babylonian isḳu) is still uncertain as none of the existing proposals is sufficiently convincing.
The West Semitic origin of the word was first proposed by Ebeling 1952–1953:215, who connected it with the Rabbinic Hebrew plant designation prḥlbn in DTTM 1223, where it is interpreted as a “‘White Blossom’, name of an aromatic shrub”.
First, the word has been connected (Lewy 1938, 139, n. 5, Bilgiç 1954, 75, Haas 1977, 81) to the Hittite name of the festival purulli (CHD 391). The second suggestion (Richter 2004, 264 f., n. 7) is to compare it to Hurrian pur(ul)li “temple” (GLH 206, BGH 329). Both comparisons are based on a clear-cut phonetic similarity, while the obvious semantic difference is left unexplained (that the functions of the purullu-official were connected
with the purulli-festival, as suggested in Haas 1977, 81, is merely an etymological guess). As an alternative, a comparison with Hurr. furullinni/prln “diviner” (BGH 327, 536) can be surmised, in spite of the functional difference between the two types of personnel.
If the reading of the verbal form in question as tupaṣṣa ‘you crush’ (CAD) is accepted, the Akkadian lexeme can be compared with several WS verbal roots (see EDA I). Still another possibility is to consider Akk. puṣṣû to be a variant of paʾāṣu (pâṣu) ‘to crush’.