Latin delta (ẟ) is a Latin letter similar in appearance to the Greek lowercase letter delta (δ), but derived from the handwritten Latin lowercase d. It is also known as "script d" or "insular d" and is used in medieval Welsh transcriptions for the [ð] sound (English th in this) represented by "dd" in Modern Welsh.
A proposal to include several medieval characters in the Universal Character Set included this character with the name LATIN SMALL LETTER SCRIPT D. This was renamed to LATIN SMALL LETTER DELTA and added to Unicode as U+1E9F when Unicode 5.1 was released on 4 April 2008.
References
Latin delta Wikipedia(Text) CC BY-SA