The main anagram of his name is "another" and that certainly has its theme represented pretty obviously throughout the whole series.
"No heart" also can be taken metaphorically, as Sora2016 says, for his usual modus operandi of treating other hearts just as tools/pawns to further his own ambitions, not to mention that by now both Ansem the Wise and Sora have called him out on his immense ignorance on how hearts actually work despite his claims otherwise.
Xehanort sees and accepts only the properties and traits a heart has that further his own interests and also happily produces wounds, scars and traumas left and right regardless of who is unfortunate enough to get into his sights as long as it furthers his ambitions, No heart is a fitting pointer for such a behaviour.
The whole Nobody-thing is also a stale thing by now since as of current lore canon Xehanort cannot have created any further Nobodies since he never turned into a Heartless that could have produced one.
When he did create a Heartless (Ansem SoD) the Nobody corresponding to this one (Xemnas) is already known.