Genèse 16:11

And the Angel of the Lord said to her, Behold, thou art with child, and thou wilt bear a son, and thou shalt call his name Ishmael, because thy affliction is revealed before the Lord.

AND THOU SHALT CALL HIS NAME ISHMAEL. The angel informed Hagar that his name will be Ishmael — just as in the verse, Behold, a son shall be born unto the house of David Josiah by name — and he told her that she should so call him, and thus remember that G-d heard her affliction. (G-d heareth) is, as the angel explained to Hagar, “because the Eternal hath heard thy affliction.” (Verse 11.) Now Abraham either called him by this name on his own,. with the intent that G-d hear him and answer him, or the Holy Spirit rested upon him, as Rashi has it, and he called him Ishmael because G-d had heard his mother’s affliction, as the angel had said.
The correct interpretation appears to me to be that the angel commanded Hagar that she call him so, but she, being a concubine, was afraid to give a name to her master’s son, so she revealed the matter to him, and Abram fulfilled the word of G-d. Scripture, however, did not need to delve at length into this matter.

ויאמר ... הנך הרה, the angel used these words as an introduction, seeing he was well aware that Hagar knew that she was pregnant as the Torah had reported in verse 4, as well as Hagar's reaction. The message that angel had come to deliver was וילדת בן, "you will give birth to a son." The word יולדת is a composite composed from the word וילדת, which is a verb in the past tense converted into the future tense by the letter ו at the front, the other component being the word ויולדת, the same root as a present participle. The meaning of the combined composite is that seeing that the birth was something that had not yet occurred, the verb must contain an allusion to the future, whereas seeing that Hagar knew that she was pregnant, i.e. that the process which would result in a birth had already begun, the formulation of the verb had to reflect this fact also. The angel's message was: "just as you are aware that you are pregnant you should be equally aware that you will bear a son as a result of this pregnancy." There are some grammarians who believe that the root of the word here is similar to a four-lettered verb.

וקראת שמו, the letter ת at the end is a feminine ending future tense, i.e. "you will call." On the other hand, in Deut. 31,29 the same word וקראת אתכם refers to a third person feminine construction where the letter ת substitutes for the letter ה, the expression meaning: "it will befall you." The reference is to the רעה, evil, a noun that is feminine which follows immediately after the word אתכם.

אל עניך, "to your outcry [complaint instead of prayer, Ed.] concerning your plight." We are forced to explain the angel's words in this fashion, seeing he spoke of G'd having "heard," שמע, instead of ראה, "G'd has seen." It is also possible to explain the angel's words as does Onkelos, i.e. as צלותיך, "your prayer." There are precedents for the word ענה meaning a response to something, to wit Job 3,2 and Isaiah 13,22 as well as Deuteronomy 26,5 וענית ואמרת, and similar examples.