I realize that POS is a term that is widely used as a TLA for point of sale, but it feels like Shopify POS is an unfortunate name given that it's also a TLA for piece of sh*t.
POS is the standard industry term for this kind of software. Anybody who would actually buy this product would never mistake this. And anyone who might mistake it for the other meaning needs only to click through to see it is indeed a POS system.
As other's have said, it's an industry standard term. Whilst in acronym heaven, I actually had to look up what TLA meant. Three Letter Acronym for those wondering.