In John Keats's poem La Belle Dame sans Merci, he writes, "She looked at me as she did love,/ And made sweet moan." Keats seems to use the word "moan" in a similar sense in the third stanza of Ode to Psyche: "Nor virgin-choir to make delicious moan/ Upon the midnight hours." In the fourth stanza, Keats again uses the phrase make moan. I noticed that in other poems, Keats employs the word "moan" in the typical sense. For instance, in thirty-third stanza of The Eve of St. Agnes, he describes Madeline uttering a "soft moan" as she gains consciousness. This usage seems more or less descriptive.
I was surprised that the very stanza where I found this example also had a reference to the song "La belle dame sans mercy." I read that Keats wrote The Eve of Saint Agnes before La Belle Dame sans Merci, so I know that he is not referencing himself. But I find it odd that Keats would use the phrase "make moan" in more than one of his poems. Perhaps this is a Spenserian usage, because Spenser's Faerie Queene deeply influenced Keats, and Keats deliberately used archaic words like Paynim to mean a (usually Muslim) non-Christian or wight to mean "person" (as did many poets, but Keats seemed particularly connected to Spenser).
Some online forums such as this one attach a sexual meaning to the word "moan." While these websites aren't authorities on Keats or English usage, I have to admit that the word "moan" certainly suggests sexual activity, just as other questions about "moan" on English Stack Exchange.
Another website claims that the phrase "made sweet moan" is just for poetic assonance. I will post the other two links as a comment because this is my first question, and I lack the reputation needed to embed more than two links.
I doubt that Keats intended the word to be sexual - it makes little sense in the context of "virgin-choir" or the overall mood of these poems. I was just wondering if there was an obscure or archaic usage of "moan" that would make sense in context. Thank you!