Yitschaq

Yitschaq means he laughs

from tsachaq meaning laughter, play, make sport 

from a primitive root word meaning to laugh outright (in merriment or scorn)

Then Abraham fell on his face, and laughed, and said in his heart, "Will a child be born to him who is one hundred years old? Will Sarah, who is ninety years old, give birth?"... God said, "Sarah, your wife, will bear you a son. You shall call his name Yitschaq. I will establish my covenant with him for an everlasting covenant for his seed after him. ... But my covenant I establish with Yitschaq, whom Sarah will bear to you at this set time next year."(Bereshit 17:17,19,21) 

Yitschaq’s name comes from what both his mother and father did when they learned that Sarah would be having a son at ninety years old, not from an indication that his life would be  filled with humor. His purpose was set, regardless of the name given him.

By extension, it also refers to a verse in Tehillim (37:12-13) The wicked plots against the righteous and gnashes at him with their teeth. But, Adonai laughs at him, for he sees his day coming. Yitschaq was the seed of promise that would eventually bring about Yeshua, and his birth set in motion the plan of salvation. This is the day that Adonai saw coming. 

Rivqah

Rivqah means to tie firmly, a connection, a link, secured

from an unused root meaning to bind by tying up the fetlock; fettering (by beauty); by extension, a binding, an agreement, a joining together

He said to them, "Don't hinder me, since Yahweh has prospered my way. Send me away that I may go to my master." They said, "We will call the young lady, and ask her." They called Rivqah, and said to her, "Will you go with this man?" She said, "I will go." They sent away Rivqah, their sister, with her nurse, Abraham's servant, and his men.(Bereshit 24:56-59) 

She said to the servant, "Who is the man who is walking in the field to meet us?" The servant said,"It is my master." She took her veil, and covered herself. The servant told Yitschaq all the things that he had done. Yitschaq brought her into his mother Sarah's tent, and took Rivqah, and she became his wife. He loved her. Yitschaq was comforted after his mother's death. (Bereshit 24:65-67)

The Rivqah in Scripture served her name well, by agreeing to go with Abraham’s servant, and then joining together with Yitschaq to become his wife. When it came time for Yitschaq to bless his elder son, she made sure that Yaaqov got the blessing. Some have faulted her for this, but I believe she acted out of the knowledge that was given to her by YHVH, which was a binding agreement between the two of them.