源
=
原
+
氵
:
The origin (源) of the H bomb can be traced back to when Yu the Great (yu) once forgot a lot of water bottles (氵) next to her A bomb (原) in the anthill's kitchen (an2) and accidentally detonated the bomb.
汇
=
匚
+
氵
:
Helga Horse (hu) brought a collection (汇) of water bottles (氵) and a metal box (匚) to the Eiffel Tower's bathroom (ei4). Each bottle contains water from a different river. Finally the moment she's been waiting for arrives: As she empties each bottle into the metal box, she converges (汇) the water of all these rivers at once.