Who bestowed the Honorific title Mahatma on Gandhi?

Rabindranath Tagore, a Bengali poet and greatly honored man of arts and letters. He was the first non-European, and only Indian, to be awarded the Nobel Prize for Literature (1913). Although he considered Gandhi a "great soul" (mahatma), his relations with the man were tumultous as they disagreed on a number of things, though these tended to be more political than philosophical.