Traditionally analysed as a doubling of tree 木 and an abbreviation of the no longer used character 𩰪 acting as phonetic. However, it seems more likely that 𩰪 was a variant of 鬱.¹ Older forms show a doubling of tree with a crouching or standing figure, or both: 
. The original meaning of 鬱 seems to have been dense (forest) but was early on also used for fragrant / aromatic wine. To clarify the latter meaning vessel with rice wine 鬯 and 彡 (expressing the fragrance) were added.² ³ Also the standing 大 figure was replaced with earthenware vessel 缶 and the crouching figure transformed into 冖. The original meaning evolved to obstructions, pent up feelings and being depressed or anxious. Suggest taking 匕 as fallen or lying person and 彡 as hair.
Mnemonic: Lying between the trees with a can of rice wine, hands in my hair, I feel depressed
The Oracle bone characters seem to show a doubling of 木 with either a standing or a crouching figure (or both) among them.
 |
 |
 |
 |
 |
At an early stage the meaning of 鬱 seems to have been ‘dense’ and perhaps ‘luxuriant’, but according to Ochiai it got also to be used to write the word or name of an aromatic or calming drink. Ochiai thinks it was this usage that inspired scribes to later add vessel with rice wine 鬯 and 彡 to express fragrance or aroma.[3] The transformations at the seal characters stage (大 to 缶 and the crouching figure to 冖) seem plausible giving that a lot of characters underwent remarkable changes during the of process standardisation.
Following 許慎 Xu Shen, traditionally 𩰪 is proposed as phonetic in 鬱 (abbreviated, with hands left and right replaced by trees). Ochiai analyses 鬱 as consisting of semantic elements only and doesn’t even mention 𩰪. This database shows the sealscript version of 𩰪 as a variant of 鬱.
Another variant of 鬱 is 欝, which seems to be an confusion with 爵, originally an elaborate depiction of a large ceremonial wine vessel on three legs (see Henshall 1344). Yet another variant is 鬰, which like 欝 replaces 缶 with two simple crosses. Wieger (130 E) shows a third variant, which replaces 罒 with 冖 but is otherwise identical to 欝. It seems safe to conclude that the scribes had difficulty with this character.
Two other characters can be connected with 鬱. At some point 蔚 seems to have been used to write a similar or even the same word as that 鬱 was used for (Schuessler, p. 592). 蔚 exists in Japanese, but seems rare. There is an archaic word ō-utsu 蓊蔚 ‘overgrown; exuberant; lush’ and hin-utsu 彬蔚 ‘erudite and refined; handsome’. These words are totally forgettable, but it’s interesting that these words clearly have the ‘thick growth’ connotation, and that 蔚 is pronounced as utsu, just like 鬱.
In the PRC 鬱 has been completely replaced by 郁. Originally 鬱 and 郁 pointed to different words, both meaning ‘fragrant’. According to Qiu (p. 361) due to sound changes 鬱 and 郁 came to overlap in pronunciation as well as their meaning. With the latest character reform 郁 is now used to write 鬱 in words that carry the other meanings of 鬱 (melancholy etc.) also (places like Hong Kong and Taiwan still use 鬱 as in Japan).
Wieger states that 鬱 originally pointed to ‘thicket, brushwood’ which by extention lead to ‘onbstruction, hinderance’. Schluessler references one old Chinese meaning of 鬱 as ‘a fragrant herb’ on p. 592, and a bunch other meanings on p. 513: ‘be dense’ (forest) > ‘to block up’ > ‘pent up’ (feelings), ‘oppressed’, ‘depressed’, ‘anxious’. The meaning of ‘anxious’ is ancient, it is already used with that meaning in 孟子 Mengzi (Mencius, 371-289 BCE).[4]
Here are two attempts at a mnemonic:
