Where does “tangalog” come from?

tangalog (Tagalog) comes from Tagalog Tagalog, from Tagalog ilog, from Proto-Philippine *iluʀ, from Proto-Malayo-Polynesian *iluʀ, from Proto-Austronesian *iluʀ — river channel.

Ancestry of “tangalog”, step by step

tangalog traces back through two separate lines of ancestry.

via Tagalog Tagalog

StepLanguageWordMeaning
1TagalogTagalogThe Tagalog language; To speak in the Tagalog...
2Tagalogilogriver
3Proto-Philippine*iluʀriver
4Proto-Malayo-Polynesian*iluʀriver
5Proto-Austronesian*iluʀriver channel

via Tagalog tanga

StepLanguageWordMeaning
1Tagalogtangagullible; idiotic; stupid; foolish
2Proto-Philippinetaŋato gape stupidly; to gawk
Every word from Proto-Austronesian *iluʀ →Every word from Proto-Malayo-Polynesian *iluʀ →Every word from Proto-Philippine *iluʀ →