When used as a verb, the word pin means to fasten or attach with a pin. Another meaning for pinned is held down or trapped.
Ex: Jeannie looked lovely at the dance, all in pink. She had pinned a small corsage to her dress, and even the flowers in it were pink.
Ex: After the landslide was over, Mark realised that he was pinned by a boulder that had become dislodged. He didn't think he was hurt, but he could not get his leg out from between the boulder and another rock no matter what he did.
If you want to indicate that you have found specific information on some issue or question, you can say that you have pinned it down. If you pin someone down, you are pressing them for an answer to a question.
Ex: The insurance company has spent weeks trying to pin down the cause of the accident, and finally, yesterday, they made a breakthrough.
Ex: It was impossible to get an answer out of Jules. He never returned my phone calls and would avoid the issue whenever I saw him. Finally, one day, I stopped at his place of work and pinned him down on the answer.
A bow is a symmetrical type of knot, commonly used to tie shoes and decorative ribbons.
Ex: When teaching my young son to tie his shoes, I decided to teach him how to tie a bow, since it is the simplest type of knot.
Ex: When I saw my twin nieces at Christmas, I couldn't believe how cute they looked, in matching dresses and with matching bows in their hair.
If you want to say that something has been done for someone else completely, you can say that it has been tied up in a bow. The idea is that whatever you have done is like a present you are giving someone. A typical way to refer to the frilly styles of female fashions is buttons and bows.
Ex: Detective Krankenhaus solved the case this morning. By this afternoon, the suspect was in custody, the evidence had been analysed, and the report was written. Captain Rilke said that Krankenhaus had tied the case up in a bow.
Ex: The day Julie got married, I couldn't believe how far my daughter had come since her days of girlish buttons and bows