Abarim Publications' online Biblical Hebrew Dictionary
The verb פעה (pa'a) appears to express the contagious verbal expression of painful effort. In several cognate languages this verb describes the bleating of sheep but the only Hebrew occurrence appears in a metaphor in which YHWH says that his silence will now be followed with his groaning/wailing like that of a woman who enters labor and needs assistance (Isaiah 42:14). In the previous verse he compares his exclamation to the shout of a man of war, and both the bleating of a sheep and the rallying cry of a man of war are both intended to propagate like snakes or fire in the minds of the other sheep or warriors.
The derivations of this verb are:
- The masculine noun אפע ('epa') of unclear meaning. It occurs only in Isaiah 41:24, where it describes the inevitable fate of worthless work. BDB Theological Dictionary insists that this word came about due to a scribal error, and should actually say אפס ('epes), meaning a ceasing, but it rather describes a fad that may have gotten some traction but eventually fades out due to its lack of practical applicability.
- The masculine noun אפעה ('epa'a), which at first sight appears to describe a kind of viper (Job 20:16, Isaiah 30:6 and 59:5 only). But since the entire Bible describes human mentality, psychology, sociology and the quest for the knowledge of the laws of nature, the snake describes mental herd behavior: the believing and passing on of something, simply because it entices or in this case fills with dread rather than stand up against falsification. Note that this noun is identical to the form the verb assumes in Isaiah 42:14.