@AndrewSavinykh Oh no, that was never the reason. APL grew out of math, by rationalizing mathematical notation. THis naturally led to single mnemonic glyphs. A huge benefit is that APL has no reserved words. Also, people who do not share a common human language can still communicate algorithms. I learned som German by reading a German APL book!
The primitives of APL are very generalized, and it is wrong to assign a single name per glyph. Rather, when reading APL, one reads each symbol as appropriate in the context. Furthermore, having more code in less space reduces the risk of bugs.