Thank you for all who replied, and especially to Simon Ommanney for
pointing me to Heather Ross at the GNBC Secretariat, NRCan. Her
reply, an interesting historical reference in its own right:
Our data base record for Tweedsmuir Glacier, contains the following
"Submitted by Bradford Washburn, director of Museum of Science and
member of National Geographic Society expedition in 1935 after Lord
Tweedsmuir, John Buchan (1875-1940) Governor-General of Canada,
The name became official in 1961, according to the same record.
Many of you found references to the naming of the North/South
Tweedsmuir Provincial Parks in BC (also named after Lord
Tweedsmuir), but the glacier is not in the park - it straddles the
BC/Yukon border about 1000km the north.