From the 2 letter Arabic
root verb Sad'Lam, meaning connect.
The 2 letter root verb 'Sal' can be manipulated in many ways by adding accent marks and it all means connect.
Silato al walidain = Connecting to parents. (being good to them and honoring them).
Hamzat Wasil = Accent mark used on top of letters and give them an 'OO' sound.
A'sil = origin.
Fa-sil and Fa-sal = negative of sal and sil, meaning break.
Salat = Connecting to Allah