Playing a guitar laid flat and using a bar to slide up and down the strings has been common in the Hawaiian Islands for well over a century. The exact beginnings are unknown but it gained popularity as a playing style in America in the 1910s with the boom popularity of Hawaiian influenced music. Another boost came after World War II servicemen returning from stations in the Pacific brought this "new" idea with them.
Hawaiian guitar became something of a craze for a while. This encouraged manufacturers like Hermann C. Weissenborn and Chris J. Knutsen to develop their own instruments for the growing market. It is the surviving examples of these instruments that are the most coveted by players and that provide the most inspiration to current manufacturers.
Using a slide, often a pocket knife or a broken off bottle neck (an alternate name for the style) on a regular guitar has been documented from the early days of the blues. The composer W. C. Handy, whilst waiting at a train station in Mississippi, witnessed an unknown player who left a lasting impression on him. "As he played, he pressed a knife on the strings of the guitar in a manner popularized by Hawaiian guitarists who used steel bars. The effect was unforgettable."
Lap slide guitar - Wikipedia
"Lap slide guitar" "Lap-style guitar" "Lap steel guitar"といろいろと呼び方はあるようだが、guitarを膝の上に寝かせて、演奏する手法のことだ。
Blues、Country Bluesなどでは、よく見かける演奏法だけれども、これって、Hawaiian guitarにそっくりだなーと以前から思っていたが、調べてみると、やっぱり、rootsは、Hawaiian guitarにあるらしい。
弦に金属的なものを押し当てて上下に滑らせるHawaiian guitarの演奏法が、BluesのSteel guitarの演奏法と非常に親和的だったのだろう。その演奏法が、Bluesの中に取り入れられていって、今のLap-style guitarの形が出来上がっていったようだ。