Hannah did the unthinkable.  She was so despised, so humiliated, and felt so un-woman-like that she petitioned God constantly for a child.  While we celebrate Motherhood, Hannah is not your typical candidate as a celebrant of this significant honoring of mothers.
No matter how Elkanah tried to appease her, she was relentless in her request to God, not for motherhood, BUT for womanhood.  In Jewish society, to be barren was almost to not be a woman.  Reproduction was more important than recreation.  No one really cared too much for the activity of sexual intimacy.  What really mattered was the fruit, the outcome- pregnancy.  That proved womanhood more than anything else.
To be barren was to be considered as cursed.  Hannah wanted to proof, evidence that she was a woman.  That would come only through childbearing.   So she pursued Divine aid through bitter tears.   Eventually she bargained with God.  So to God she bantered- “If you would give me a son ( evidence of womanhood),  I would give it to You (sacrifice of motherhood).”
God heard her.  She conceived.  She was a woman- WHEW! ! !  FINALLY! ! !.  Now she will keep her word, her end of the bargain.  She waited until Samuel was weaned, then she shipped him of (motherhood rescinded) to the House of the Lord to be raised in and for the service of God.  Motherhood was sacrificed fore Womanhood.