Ki Teitzei: Taking the Mill or Upper Millstone to Pledge

In Devarim 24:6:

ו לֹא-יַחֲבֹל רֵחַיִם, וָרָכֶב: כִּי-נֶפֶשׁ, הוּא חֹבֵל. {ס

6 No man shall take the mill or the upper millstone to pledge; for he taketh a man's life to pledge. {S}

What is this nefesh hu chovel? A standard explanation (see e.g. Rashi, citing Bava Metzia) is that it is used for preparation of food, ochel nefesh, and one should not take that as a pledge. Thus, Rashi:

One shall not take the lower or the upper millstone as security [for a loan] If [a creditor] comes to the court to demand security for a debt [for which no security had previously been required], he may not take as security articles used in the preparation of food. — [B.M. 115a]

Another explanation is that it is poetic overstatement. You are taking his livelihood. How will he make more money to repay his loan and get his pledge back? You are thus taking his life as a pledge.

Indeed, I would put forth that perhaps chovel is a pun. It means "take as a pledge," but it also means "wound, injure." Thus, he is wounding the fellow's life, by taking this pledge.