Short answers, pulled from the story.
William Labov founded the field of variationist sociolinguistics in the 1960s. His work in New York City department stores demonstrated that language is a living reflection of social class and identity rather than a static artifact.
The observer's paradox is the problem where the presence of a linguist causes subjects to alter their speech patterns and speak more formally than they would naturally. Researchers solve this by asking interviewees to recount traumatic events or by interviewing multiple subjects together to elicit natural vernacular speech.
Basil Bernstein defined the restricted code as language that relies on extraverbal communication and shared context, while the elaborated code emphasizes verbal communication and requires a broader lexicon. The restricted code thrives in environments with strong social bonds, whereas the elaborated code is typical in settings where social roles are fluid.
The first attested use of the term sociolinguistics was by Thomas Callan Hodson in the title of his 1939 article Sociolinguistics in India published in the journal Man in India. Modern study of the social aspects of language began earlier with Indian and Japanese linguists in the 1930s and forerunners in Denmark and Switzerland around the turn of the 20th century.
Covert prestige is a phenomenon where standard language is considered undesirable in certain traditional working-class neighborhoods because it signals a lack of loyalty to the community. Individuals may exaggerate non-standard features to express neighborhood pride and class solidarity while switching to standard varieties in professional settings.
Social networks influence speech patterns because the looseness or tightness of a community affects how members interact and adopt specific linguistic features. For instance, speakers in dense Cajun Louisiana communities were more likely to pronounce English th as t if they participated in relatively dense social networks compared to those in looser networks.