During the Blocksize War, the "small blockers" adopted a practice of calling Bitcoin Cash "Bcash". This is an attempt to obscure the history of Bitcoin and reduce the legitimate claim BCH has to the powerful and recognisable "original" Bitcoin branding. This is one part of a pattern of censorship and disinformation against Bitcoin Cash. To increase this effort, "small block"/BTC proponents registered a lot of domain names, Twitter handles etc. under the "Bcash" name to further misdirect curious individuals investigating Bitcoin Cash. This poisoned the name forever, as the real Bitcoin Cash community has no way to correct or update any lies posted via those channels. Read more about this here.
Despite years having passed since the split, BTC advocates continue with this same played-out smear campaign, indicating very strongly that they remain hyper-aware of Bitcoin Cash and its continued potential to reclaim the Bitcoin title. This is further evidenced by the lack of an equivalent deliberate pejorative used to marginalise other (smaller, less threatening) Bitcoin fork communities.
In response, the Bitcoin Cash community either ignore this labelling, or tries to educate new users in the case the intent appears to come from ignorance rather than time-wasting malice. It is critically important the community does not fold to this "rebranding suggestion", and remains defiant and adamant about its brand. This retains historical context and signals to outside observers that the BCH community can withstand any amount of disinformation or propaganda without compromising the mission of becoming the global reserve currency.
Some Bitcoin Cash advocates disagree this relabelling is a problem, and happily use the term "Bcash" - either because they think it sounds marketable or that it "takes the sting out" of it as an insult. Being a decentralised, permisionless currency those adopters are free to call Bitcoin Cash however suits them and it's not "wrong", but the majority of BCH adopters understand the central importance of preserving Bitcoin Cash's authentic brand and dislike this practice.
In general, the community prefers the names "Bitcoin Cash", "BCH" or simply "Bitcoin" when talking within the community or to anyone who understands the history and why Bitcoin Cash is the real Bitcoin.
See also: Should (or will) Bitcoin Cash rebrand?
See also: What happened with /r/btc?