When we say that we have "scratched the surface" of a topic or issue, we mean that we have only just uncovered the most superficial aspects of it. But why is "scratched" spelled with a "ch" instead of a "tch", as in catch? This is because the "tch" sound only occurs when the /t/ and /ʃ/ sounds are separate phonemes. In the word "scratch", however, they are part of the same phoneme /ʃ/, which is why it is spelled with just one "t".
"Scratched the surface" is an idiomatic expression that is used to describe a situation where someone has only explored or analyzed a superficial or preliminary part of a subject matter, issue, or problem, thereby failing to fully comprehend its depth, complexity, or intricacies. It implies that the person has only made a minimal or cursory attempt to delve into the matter, leaving much more to be discovered or understood.
The phrase originates from the image of physically scratching the surface of an object, such as scratching the surface of a painting or scratching the surface of a scratch card. It connotes an attempt to glean information or gain insight about something without really penetrating beneath the surface layer. It suggests that despite initial efforts, much more in-depth exploration is needed to gain a comprehensive understanding or uncover hidden aspects.
By using "scratched the surface," one implies a limited scope of knowledge or understanding, emphasizing the need for further exploration, research, or analysis to truly grasp the complexities beneath the surface. The phrase is commonly used in conversations, discussions, or writing to highlight the need for deeper investigation, acknowledging that the initial exploration has only touched upon the most basic or superficial elements of a complex matter.