“Love” according to the DPR comes from the root mid, which can also mean to be fat… I assume to grow fat with goodwill. It’s not clear how mid can be put into metta, at least for a basic n00b like myself, and the DPR is confusing regarding it:
metta
n c
mettā: amity; benevolence. (f.)
Metta (adj. nt.) [cp. Vedic maitra “belonging to Mitra”; Epic Sk. maitra “friendly,” fr. mitra] friendly, benevolent kind as adj. at D iii.191 (mettena kāya – kammena etc.), 245 (˚ŋ vacī – kammaŋ); as nt. for mettā in cpds. of mettā (cp. mettaŋsa) and by itself at D i.227 (mettaŋ+cittaŋ), perhaps also at Sn 507.
Above is how Bhante G translates Metta, and explains it as coming from the said root, there is no “love” or “loving” in this translation… now however if you DPR mett(Ā) this is what you get:
mettā
n c
mettā: amity; benevolence. (f.)
Mettā (f.) [abstr. fr. mitra=mitta, cp. Vedic maitraŋ. According to Asl. 192 (cp. Expos. 258) derived fr. mid to love, to be fat: “mejjati mettā siniyhatī ti attho” love, amity, sympathy, friendliness, active interest in others.
The way I read this basically is that two different scholars or scholarly works (who/what is ASL?) say different things, and its kind of up to yo to decide what works within the context of the teachings.
I greatly prefer the Thanissaro Bhikkhu translation of “boundless/limitless goodwill”, as imo it fits much more with what the Buddha was saying in the suttas, and you don’t have to spend extra time explaining all the reasons why metta does not equal the english word love, which is Pema
Pema (nt.) [fr. prī, see pīṇeti & piya & cp. BSk. prema Jtm 221; Vedic preman cons. stem] love, affection
EDIT: I also agree with Bhante Analāyo in that " like a mother protects her only child" means that you protect your metta, because a mind without metta sucks and is downright oppressive and it makes much more sense given the rest of the suttas where the Buddha takes seriously the harm a mind of ill-will can do. Bhante G also says the same thing as Bhante Analāyo regarding this particular phrase.