At last I have an answer. Here is how it goes:
1) I have already created Origin account with email [edit: email address removed] and password "xxxxxxxx"
2) Now I want to have SWTOR account created under my existing Origin account
QUESTION: Will I get new Origin account when I register on SWTOR site?
ANSWER: NO! 🙂
3) I created account on SWTOR with password "yyyyyyyy"
4) After registration I entered to the account information and entered e-mail [edit: email address removed]
5) I did not receive any validation email on [edit: email address removed] adress
6) On SWTOR account I entered email [edit: email address removed]
7) I received validation email on adress [edit: email address removed]
Now your newly created SWTOR account is binded to your Origin account, where you did not get any new Origin account (I checked it) and your Origin password "xxxxxxxx" has been replaced with SWTOR password "yyyyyyyy".
PS: Strangly I did not get any new Origin account where I remember that year ago creating SWTOR acc brought also new Origin acc.
PS2: SWTOR and EA support should know this mechanic for the future.