Like many things regarding the Python language, "Unladen Swallow" is a Monty Python reference, specifically to the gag about the airspeed velocity of unladen swallows in Monty Python and the Holy Grail.
Steve Swallow | Red-rumped Swallow | Swallow the Sun | Swallow | James Swallow | Swallow Tanager | Northern Rough-winged Swallow | White-rumped Swallow | Swallow TP | Swallow This Live | Swallow-tailed Kite | Swallow Sidecar Company | Swallow New Swallow | Ian Swallow | The Big Swallow | Tell Me What Rockers to Swallow | Swallow This Live: Flesh & Blood World Tour | Swallow Tales | Swallow-tailed Hummingbird | Swallow My Pride | Swallow Falls | Swallow Doretti | Swallow (bird) | Swallow Airplane Company | swallow | Southern Rough-winged Swallow | Sea Swallow | Jerod Swallow | ''Ganggyeong'' (''Swallow'') class | Ethiopian Swallow |