Pentecost and Whitsun

I found myself wondering about the etymology of 'Pentecost' and 'Whitsun' today. 'Pentecost' is just about the earlier of the two words in English.

To be absolutely accurate, 'Pentecost' is recorded in various early Old English texts, 'Whit Sunday' is first recorded in c1100 and 'Whitsun' is first recorded in 1297. Here's the Whit Sunday reference: "On þisan Eastron com se kyng to Wincestre, & þa wæron Eastra on x kal. April, & sona æfter þam com Mathild seo hlæfdie hider to lande, & Ealdred arcebiscop hig gehalgode to cwene‥on Hwitan Sunnandæg." (The Anglo-Saxon D Chronicle for 1067)

The epithet 'white' in 'Whit Sunday', according to the wonderful Oxford English Dictionary, "is generally taken to refer to the ancient custom of the wearing of white baptismal robes by the newly-baptized at the feast of Pentecost".

'Pentecost' - "Judaism. The harvest festival observed on the 6th Sivan, fifty days after the offering of the Omer on the second day of the Passover. Also: a synagogue ceremony held on the same day to celebrate the giving of the Torah on Mount Sinai." - by contrast, derives from the post-classical Latin 'pentecoste'.

I suppose a discussion about pentagons, pentameter and Whit, the minor character from Of Mice and Men who will one day have a GCSE question all of his own, would be my way into this topic.