In the last 50 years the bodhrán has changed and developed like no other instrument in irish music, maybe even like no other instrument at all. What happened before the last  years?

Origin
The Bodhrán is a frame drum. Frame drums are found in different forms all over the world. The origins are uncertain, although there is an obvious similarity to the tambourine, that is found in the south of continental Europe. It migh have come to Ireland through trade routes, but there is no final proof for that. There is also no proof for the use as a war drum, I have no idea where that thought comes from.

The name „Bodhrán“ comes from the irish word bodhar, meanig deaf, dull or numb. THe word Bodharaí stands for a hollow sound, the sound of a drum etc. The English word "to bother" derives from "bodhar", which is not in use anymore in today Irish.

The earliest proof of the use of the bhodhran goes back to a book of the 15th century. It is a medical trancript in which the sound of a bloated belly iis described as the sound of a drum (bhodhrán). In old encyclopedias the word can be found being used before 1827. Pictures of the Irish painter Maclise, that were publsihed around 1850 show a frame drum on which the left hand of the player seesm to touch the skin and the right hand seems to move in the typical way.

I also learned recently that in some areas of Kerry there are were bodhrán makers as ealry as 1920, who made drums not only for local musicians, but also as a souvenir!
In order to understand the history of the bodhran, you have to look into the history of traditional irish music. There were times when it wasn't as popular as it is today. It only came back into popularity in the 50s and 60s. In this period of time the big change from a ritual instrument to a musical instrument took place for the bodhran.

The Ritual instrument
Bevor the 50s, the bodhran was almost  played only on one occassion in the year: St. Stephens Day, the day the Wren boys were trying to cath the wren, a ritual known as "Hunting the Wren". The Wren boys used whistles and bodhran-like drums as shown on the early picture on hte left hand side. When Sean O'Riada started to bring traditional irish music on the stage he declared: "The Bodhrán is the national drum". So he opened a pathway for the drum and from there it was used in more and more bands. The drum developed further in quality and shape and even now this development hasn't finished at all. Different makers are developing and experimenting with different ideas about the skin, the tuning mechanism and the frame and a variety of dimensions can be seen nowadays.

The musical instrument
The first bodhrans were rather loud and many of them had a poor quality. The first known recording of a drum and a flute playing ITM is from the year 1927. We don't know which type of drum we hear on this recording, it may be a tambourine.
In the early days the drum was played either with the hand or a stick, the other hand wouldn't touch the skin to dampen it. Sometime you would have found jingles attached to the rim. During the last decades the sound was cleared up. The jingles were removed and the sound was dampened by the left hand. Tonal variation came in with the help of the left hand on the skin. Player like Peadar Mercier, Johnny "Ringo" McDonagh or John Joe Kelly brought the drum and the playing technique to today's standard over the last 40 years.