Filipinos are not one ethnic group. Among the large ethnic groups in the Philippines are the Ilocano, Cebuano, Kapampangan, Pangasinense, Bicolano and Tagalog.
Tagalog is the name of an ethnic group in the Philippines. The language they speak is Tagalog.
The Tagalogs (the Tagalog people) speak the Tagalog language. Likewise, the Ilocanos speak the Ilocano language, and the Pangasinense speak the Pangansinan language. These are all very different languages; they are not just dialects.
Many of the Tagalog people live near Manila, the political and economic capital of the Philippines. When the 1935 constitution was drafted by government officials, they selected Tagalog as the basis of the national language.
In order not to slight the other ethnic groups, the national language was not called Tagalog, but Pilipino. Later, in the 1987 constitution, the national language was called Filipino, with an F.
The national language (Filipino) is supposed to include not only words from Tagalog, but also from other Philippine and foreign languages.
WHY PILIPINO, THEN FILIPINO?
In the Tagalog language, there is no phoneme "f." Until recently, many Filipinos had a difficult time pronouncing "f." When Filipinos say "fantastic," it may come out as "pantastik."
Those Filipinos who have been exposed to the sound at an early age through the media or education have no problem with pronunciation. In fact, a marker of your social class in the Philippines is your ability to pronounce words. If you go to Manila and slip on the "f" then you're labelled probinsyano (from the provinces; provincial).
Because the Philippines had a long history under the rule of the Spanish and the Americans, both of which had non-native letters and sounds such as "f" and "z" and "v" Filipinos use foreign words (especially English and Spanish) on a regular basis. There are many concepts that are more familiar to Filipinos in their English form than in the Tagalog translation.
For example: on a television quiz show, the contestants were asked what the native Tagalog word for 'magnet' was. Everyone understood the English word 'magnet' but only the educated ones knew that the Tagalog word for magnet was batubalani.
In another example, Filipinos have no problem understanding the English word "manager" — they use it all the time. But companies and even the U.S. government provide Tagalog documents that use the word "tagapamahala" or "tagapangasiwa" in a forced translation. Filipinos actually have a tough time determining which job title the Tagalog translation is referring to. They prefer the English word, although they may pronounce it as "manedyer."
If you listen closely to Filipinos having a conversation, you'll realize that more than half the words are in English, only that they pronounce it the Filipino way. And of course, the grammatical structure remains that of Tagalog.
There are very few Tagalog purists left who want to purge the Filipino language of its foreign elements. It's just not practical and it denies the reality of Philippine history.