“Garua” is a very popular 1943 tango by Anibal Troilo and Enrique Cadícamo. It is the second of 3 tangos produced by them both, the other two being “Pa’ que bailen los muchachos” (1942) and “Naipe” (1944).
According to a story told by Cadícamo himself, Troilo came up to him with a musical piece one night after his show at the cabaret Tibidabo. Troilo asked Cadícamo if he could create lyrics for hus music and as he walked back home that night there was a very light rain falling over him. This is where Cadícamo conceived the first verses of one of his most famous tangos. 
Sad and lonely along the road,
goes this heart striken with sadness
Like an abandoned house
Garua is a lunfardo term of Quechua origin which translates to “drizzle”. 
The rains is a recurrent theme in tango and has been evoked directly or indirectly in many other pieces such as “El café de Los Angelitos”, “El ultimo café”, “Charlemos”, “Tarde gris”, and “La noche que te fuiste” as a symbol of sadness and loneliness. 
It wasn’t long after that night under the drizzle that Cadícamo came back to the Tibidabo with “Garua”. A few days later Troilo was rehearsing with Francisco Fiorentino and the song was an instant hit. It was first recorded by Troilo and Fiorentino on August 4, 1943 under the label RCA Victor. Pedro Laurenz recorded his own version two days later with Alberto Podestá under the label Odeon.
“Garua” became a great classic of Troilo’s repertoire and in 1962 he recorded it again with Roberto Goyeneche who also had great success with it and went on recording two other versions with Raul Garello and Astor Piazzolla.
Other well known interpretations of “Garua” include those of Hugo del Carril and Adriana Varela.
 Del Priore, Oscar, and Irene Amachástegui. Cien tangos fundamentales. Buenos Aires: Aguilar, 1998. Print.
 Garúa. Tangos al Bardo, 2013. Online. http://tangosalbardo.blogspot.com.ar/2013/07/garua.html
 El tango y la lluvia. El Litoral, 2011. Online. http://www.ellitoral.com/index.php/diarios/2011/08/20/escenariosysociedad/SOCI-02.html
 Diccionario lunfardo. Todotango. Online. http://www.todotango.com/comunidad/lunfardo/?i=G&s=all