Put the year and model number of your vehicle in your info and also post it when you ask questions.
See post 2 in the below thread. The rounded bulbus male end I have only read it refried to as an Acorn. However, that is a shop name. Nothing in my 18 years as a diesel mechanic in my experiences uses those but Mercedes.
I have seen a Choline chart where they sold the fittings but don't remember the real name for it.
The threaded end on the Oil Cooler is referred to here on the forum as the Oil Cooler nipple.
The Nipples used to repair the oil cooler nipples are actually the fittings at the base of the Oil Filter Housing that the Oil Cooler Hose screws onto. They have a name and are called screwed nipple.
Oil cooler nipple size and pitch
The ones in the attached picture were listed as conical hose nipples in a catalog. It sells Choline products (Choline Oil Cooler Hose is used on many aftermarket oil cooler hoses including the ones for Mercedes).
https://www.newcoproducts.com/index.php?route=product/category&path=328