"The Rumba has its roots in the Cuban son. The Rumba consists of two quick steps and then a third slower step that takes two beats to execute. Dancers use a box-like pattern to guide their movements." - Source
This dance showcases elan, seduction and poise. Let's see how it's used in the movies.
COLLEGE SWING (1938)
The Rumba was still a new addition to American dance at this point and the song exaggerates the difficulties in performing it. However, when the kids want to be romantic and grown up, the Rumba is at hand.
NEPTUNE'S DAUGHTER (1949)
In this film, Ricardo Montalban's character uses a Rumba beat to charm Esther Williams in the song, "My Heart Beats Faster."
By the 1940s, the Rumba was everywhere in the hotspots of the U.S. When Montalban asks, "Do you know what the music is saying," Williams retorts that, yes, she does have an idea what it means. She knows all about the Rumba's seductive mood and will not be taken in. But Montalban doesn't know she knows and is left with egg on his face at the end of the song.
This maneuver is consistent with the idea that the Williams character is a tough cookie. She cannot be charmed by the usual trickery. To capture her heart, frankness will work; she's suspicious of and doesn't trust herself with the pulsing beat of the Rumba.
TELL IT TO THE JUDGE (1949)
Rosalind Russell's character tries to make her ex-husband (Bob Cummings) envious by dancing with and pretending to be married to another man.
Bob doesn't know this dance and doesn't care, as long as no one else is with his ex-wife. He doesn't bother to listen to the music, just bounces around like a kangaroo. "Don't look now, but are you still wearing your snowshoes?," she asks annoyed.
Gig Young appears as that other man who can dance anything, swinging his hips to a Rumba. Rosalind Russell delights in teasing her ex-husband by dancing with the other man and keeping the emphasis on her hips by shimmying in front of a handkerchief. Her ex-husband is livid.
This time the dance is the cause of envy. The more attractive male is the one who knows how to Rumba.
In the early to mid- 20th century, the Rumba's smooth rhythms are a symbol of seduction and sophistication in the movies. Even in comedies, the dance is used to separate hip and modern people from the squares.