Historical clue formulations

• Dearest pal — 2025-08-13
• #1 pal — 2024-12-30
• Closest confidant, informally — 2024-10-25
• Closest pal — 2021-12-13
• One whom you might tell *everything* — 2021-06-04
• Closest pal — 2021-05-05
• Favoritest friend — 2020-02-03
• Number one pal — 2018-05-13
• Closest friend, informally — 2016-01-07
• Closest friend, slangily — 2014-12-14