Past Participle in fact is not past because it can be not only:
"a written letter" (the action of writing is over here, i.e., is past). For Russians: "написанное".
"a kept word" (the action of keeping may not be over at all, i.e., may be present). The "kept word" is not only the one that "has been kept" already, but also the one that "is being kept", or "has been being kept". For Russians: "сдерживаемое" (а не только "сдержанное").
So, the Participle should have rather been called Passive, not Past, since it describes Voice, not Time, and can be both past and present.
I have written the letter.
Personally, I prefer Michael Lewis's suggestions: first form for the base, bare-infinitive, dictionary-entry form; second form for the Past Simple form; and third form for the 'past partciple'. I also like ING-form for the 'present participle' and 'gerund'. This does away with any confusion that is caused by using tense/time-words such as past and present, or by such technical terms as gerund and participle. However, at present the traditional names hold sway in most published materials, and our students and colleagues may be very familiar with them. We ignore them at our peril.