Thunchaththu Ezhuthachan, a poet from around the 16th century, used Arya-eluttu to write his Malayalam poems based on Classical Sanskrit literature. For a few letters missing in Arya-eluttu ("ḷa", "ḻa", "ṟa"), he used Vatteluttu. His works became unprecedentedly popular to the point that the Malayali people eventually started to call him the father of the Malayalam language, which also popularized Arya-eluttu as a script to write Malayalam. However, Grantha did not have distinctions between "e" and "ē", and between "o" and "ō", as it was as an alphabet to write a Sanskrit language. The Malayalam script as it is today was modified in the middle of the 19th century when Hermann Gundert invented the new vowel signs to distinguish them.