In shul, if a guest is honored with an aliyah, I watch as the gabbai walks over (or sends someone) to get the guest's name, then call that same person up by that name. Once the guest has been told which aliyah he is getting, why is he called up by name? He knows he is getting the aliyah.
At first, I thought it might have developed from situations where the person getting the aliyah doesn't know he will be called up -- the Shulchan Aruch speaks of a situation where a person is called up but cannot take the aliyah because he is still catching up in his davening or isn't there (Orach Chaim 135:11, Be'er Heitev 19) and he wouldn't walk out or start davening if he knew he was to be called up.
But this can't be the case because the Shulchan Aruch speaks of situations where the person called up is doing the laining himself and is required to have practiced it before hand, so he must know he is to be called up and the name is unnecessary.
Then I read about situations where the person called up is not called up by name (141:6) so there must be something significant about the mentioning of a name. As far as I could find, the only mention of the practice is in the Ramo who says on Orach Chaim (139:3):
אפילו ראש הכנסת או חזן לא יקרא עד שיאמרו לו קרא ונהגו ששליח ציבור כשרוצה מברך וקורא בלי נטילת רשות משום דהוי כאילו משעה שמינוהו לשליח ציבור הרשוהו על כך.
הגה: ובמדינות אלו אין נוהגין כן ואין החזן עולה רק כשהסגן אומר לו לעלות אבל אין קורין לו בשמו כמו שאר העולים שקוראים אותם בשמם פלוני בר פלוני ומי שאביו מומר לעבודת כוכבים קורין אותו בשם אבי אביו אבל לא בשמו לבד שלא לביישו ברבים
This seems to take for granted that we usually call someone up by name but I don't know what the source is for that idea or the rationale behind it. Any information or other sources would be appreciated.
Edit -- this question Must readers be called to the Torah by name? touches on the same issue and one of the answers gives a citation for the practice and some explanation but IMHO it is related and not fully a duplicate.