the.com/due diligence

means The reasonable care and investigation a person or business is expected to perform before entering a deal, signing a contract, or making a decision, so that nobody can later say they should have checked.

from A legal and financial term rooted in 'diligence,' from Latin diligentia meaning careful attention or 'loving attentiveness' (from diligere, to esteem highly or love). 'Due' here means owed or required — so literally 'the attentiveness that is owed.' The phrase hardened into its modern business sense in 20th-century American securities law, especially around the US Securities Act of 1933, where brokers had to show they'd investigated a stock offering thoroughly enough to avoid liability — care performed not necessarily out of virtue, but because the law demanded it.