pakach and pikuach nefesh

In a recent episode of his great podcast Streetwise Hebrew, host Guy Sharett reviews words deriving from the root פקח. He discusses the meaning and usage of such words as:

• פִּקּוּחַ pikuach - "supervision, inspection"
• מְפַקֵּחַ mifakeach - "supervisor"
• פַּקָּח pakach - "inspector"
• פִּקֵּחַ pikeach - "sharp, bright (person)"

As always, Guy does a great job showing how the root is used in Modern Hebrew. However, he doesn't talk that much about etymology. So let's see what I can contribute.

From a quick look at the words above, it might seem that the root פקח is related to vision (or in its expanded senses of supervision and insight). While that is a common connection between these words, that isn't the original meaning. 

The verb פקח originally meant "to open", but and in Biblical Hebrew was always used to describe the opening of the eyes (and in one case - Yeshaya 42:20 - ears). This is preserved in the usage today in the phrases פָּקַח עַיִן / פָּקַח עֵינַיִם  pakach ayin / pakach enayim. Literally, they mean "to open one's eye(s)", but figuratively they can mean "to keep an eye on, pay attention, become aware."

From here the more abstract senses we mentioned above developed, which are related to oversight or insight. (Klein adds that the root פכח - "to be sober" is a secondary form of פקח.)

One other phrase that Guy mentioned doesn't seem to fit this rule. This is פִּקּוּחַ נֶפֶשׁ - pikuach nefesh. It means "saving a life" or "(the obligation of) preservation of life." Quoting Wikipedia, Guy said it literally means "'watching over a soul." That would make sense based on the cases we'd discussed previously. But this is not the case here.

As Avineri discusses in Yad HaLashon (p. 475), the term originates in the phrase מְפַקְּחִין עָלָיו אֶת הַגַּל mifakchin alav et hagal found in the Mishna (Yoma 8:7, Rosh Hashana 4:8). In these two cases it refers to clearing a pile (gal) of rubble (to save a life in Yoma, to uncover a buried shofar in Rosh Hashana). 

In these examples, the verb פקח goes back to its early meaning "to open" - in this case to open up the pile of rubble. But since the case in Yoma refers to clearing the rubble to save a life, the phrase pikuach nefesh took on the more general sense of saving a life under any circumstances. So in Tosefta 16:13, we read that pikuach nefesh takes precedence even over the serious rules of shabbat. 

When Rashi explains that Tosefta (as quoted in Shabbat 150a), he quotes the foreign דיקומבימונ"ט - which is the Old French descombrement - "to purge, clear out, remove". (See other cases where Rashi uses that word here and here). Examining descombrement, we see that it is cognate (although an antonym) with the English "encumber", whose etymology is particularly relevant:

early 14c., "burden, vex, inconvenience," from Old French encombrer "to block up, hinder, thwart," from Late Latin incombrare, from in- "in" (from PIE root *en "in") + combrus "barricade, obstacle," probably from Latin cumulus "heap" (see cumulus).

That "heap" is the same as our "pile" - an obstacle we must remove to save a life. Avineri concludes that today the original meaning of "evacuate" has been largely forgotten and we assume pikuach nefesh only means "saving a life", which is where the mistaken etymology in Wikipedia originated.