Where did Whitsunday get its name?

White - Sunday or White Sun Day, its the Holy Feast Day and Sabbath day so bright with the light because of the descent of the Holy Spirit its fire brings light on the feast day of Pentecost and all wear white in the sanctuary as well as red for the fire. Its the 50th and last day of the Easter celebration the fullness of the Resurrection where Christ now sits in high heaven at the right hand of the Father and they both breath and send forth the spirit upon the earth.