PDA derived from the word Personal Digital Assistant, where if we interpret literally the result will be the electronic goods that become our personal assistant or with any other sentence became private secretary. You can examine one by one the meaning of two sentences, the personal assistant and private secretary; in general have the same job, right? Equally perform input the data, record and remind about our works.
The difference is only in the system, if a personal digital assistant, it was clear from the sentence contained in them have the word "digital", we just insert the data by ourselves that exist and we can take with us wherever we want for our work. Then a personal secretary to enter data manually and it is usually done by a woman, well, the woman who would write a list of work we will do and that will always remind us.
From that idea the first time the emergence of PDA, which is to replace someone write a manual or agenda. Where once people use the organizer or a secretary to record all of their activity schedules, phone numbers, or to help in remanding things that mattered to him/her.