Are the leaves stiff and leathery or soft and sappy like bulb foliage?

It think it may be used as filler in bouquets

https://www.etsy.com/listing/746436307/italian-ruscus-farm-fresh-greenery-in?gpla=1&gao=1&&utm_source=bing&utm_medium=cpc&utm_campaign=shopping_us_a-craft_supplies_and_tools-floral_and_garden_supplies-floral-floral_stems&utm_custom1=225dddf7-b276-473d-8266-c8fc3d4a225b&utm_content=bing_352012663_1310618009658638_81913651999163_pla-4585513245941161:pla-4585513245941161_c__746436307&utm_custom2=352012663&msclkid=652e20db544812fbef7b7e04fbfb6bd5

That’s why I asked about leaf texture. I thought of florists’ Ruscus but I’m not totally convinced. Looks too curly to me.

It's young foliage and substantive, but not leathery. I think it will get more leathery as it ages. I looked up Italian ruscus, but am not finding a species name.

How does one differentiate the genus Danae from the genus Ruscus our of flower?

I have also never found out what ‘Italian ruscus’ actually is. It’s often labelled R aculeatus which it clearly is not. It may well be Danae. OPs plant looks too curly to be D racemosa but it’s possible that’s due to growing conditions. I’ve only seen it as a tough outdoor plant.

The page linked to above uses the description

Italian Ruscus imported fresh from Italy

I read that as analogous to "Washington apples imported fresh from Washington" or "Idaho potatoes imported fresh from Idaho". With "Italian ruscus" not being a variety designation per se.

I believe ‘Italian‘ is part of its name, rather than an indication of source. It’s also known as Soft Ruscus in the trade but it still isn’t clearly identified as a particular species. I looked into it quite a bit since I was supposed to be doing the flowers for D.D‘s wedding. I say ‘supposed’ because the wedding was postponed by lockdown. I’ll be using Danae racemosa instead because I can get that for nothing.

I think this is just a recent division that is going to change a lot. I'd far rather it be Danae than Ruscus since Ruscus is pretty darn pokey. But I've grown Danae and this doesn't look like mine ever did. In any event, it was worth picking up for $1.

Well, that's another country heard from. That may be it!

Aha. Yes, Asparagus. I was suspicious of the curliness and the habit and spent a while looking at the Asparagus family but didn’t come across this one. I think katob‘s got it.