I know first names are usually shortened in verbal communication for reasons that I am not clear about. For example, Andrew becomes Andy.
But is it also the case for last names? If yes, what is the reason? Is it polite or impolite? For example, if I am correct, I heard once that Robinson is shortened to Robin by a third person in the US.
Shortened versions of surnames (last names) are often used as nicknames in English-speaking countries, but normally by people on very familiar terms with the person and therefore not in quite the same way as Robert might be shortened to Bob or Steven to Steve.
In my experience (predominantly British English) longer surnames such as Robinson and Brightman might be shortened to Robbo or Brighty or even extended from one sylable to two with the addition of an "o" or "y", e.g. Brown to Browny.
I would emphasise that this isn't something that would happen outside relatively close circles of friends, teammates or colleagues.
Shortened names are also known as nicknames. They're generally casual, shorter versions of a person's first name (Like Andy for Andrew), though they can be assigned based on features or characteristics, as well (Shorty, for example).
A nickname could be taken from a last name; it's feasible that George Macintosh, say, could be called 'Mac' by his friends.
There is no other reason that I can think of in which a last name would be shortened. It is not standard practice and could in fact be quite confusing!
Only colloquially and among friends. Sometimes the name is lengthened in such circumstances, For example, 'Jones' can become 'Jonesy'.
Nicknames come into use either because the original name is long and/or cumbersome and the nickname is shorter and/or catchier, or as a term of endearment.
The general rule is ask someone if they mind being called "X" before you refer to them as "X".
In various situtations, it may be normal to commonly refer to people principally by last name, such as in certain schools, military, sports, etc.
In such cases, a person's last name could easily be nick-named in time. From my experience, this occurs when the last name is long, complicated, exotic, or cool sounding.
My family name is Clifford. My dad was always called "Cliff" or "Cliffy" at work and so when I grew up, I would also "shorten" my last name as a option for what ppl could call me. However, I didn't realize that this practice is fairly uncommon in the US in 2021, and people sometimes don't know if my last name is Clifford or Cliff. To me, it's so obvious, but I guess if you aren't used to it happening, it is confusing.
Perhaps it's because Clifford is also a first name, which would lend to a natural nickname in "Cliff" or "Cliffy" and people just did that to my dad. I also wonder if it's a generational thing--ppl's names lacked the variety of today and I think that would make ppl more likely to use and be creative with nicknames. Today, it's more common for a person to ask to be called by his or her full name (William instead of Bill), so ppl would be less likely to use nicknames anyways, first or last name.
